Cell Cycle

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  • Created by: Sarah
  • Created on: 04-05-17 20:46
what phase is necesary to maintain cell growth?
G1 phase
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what makes up interphase
G1 + Synthesis + G2 phases
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what happens in the mitotic phase?
nulear division and cytokinesis
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what is the aim of the cell cycle?
to produce two genetically identical daughter cells
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why do cells need to increase in size between divisions?
they would get smaller over time
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what happens to the cell cycle without nutrion?
cell mass decreases over time
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what is the order of the phases of the cell cycle?
G1 phasse -> synthesis phase -> g2 phase -> mitosis phase
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what happens in G1?
environmental checking and growth
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what happens if the cell is in G0?
it is in a non dividing state
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what happens in the synthesis phase?
dna replication
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why is the cell cycle thought of as a clock?
only one diretion but can be stopped
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how long is the synthesis phase (dna rep)?
10-12 hours
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when can cells pause?
in metaphase
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how long can interphase be?
from 16 hours to a lifetime
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how long does the M phase last in human cells?
less than an hour
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what is duplicated in the S phase?
DNA
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what can be used to detect the S-phase in tissues and cells?
H-thymidine (autoradiography), bromo-deoxyuridine visualised by BrdU antibodies, fluroscent DNA dyes in flow cytometer of fluorscence activated cell sorter
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why is dluorscent dyes used in flow cytometry or florescence activated cell sorter?
can see DNA content of large number of cells
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what is the order of stages in M phase?
prophase -> prometaphase -> metaphase -> anaphase -> telophase and cytokinesis
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how to remember order of M stages?
PMAT
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what happens at the end of G2 phase before the M phase?
DNA has been replicated, centrosomes have been duplicated
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what happens in prophase?
sister chromatids condense, mitotic spindle assembles between 2 centrosomes
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what is the mitotic spindle made of?
MTs
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where does the assembly of spindle MTs begin in animal cells?
in the centrosome
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what is the centrosome for?
MT organizing centre
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what is an aster?
short MT that extend from centrosome away from chrs
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what does the spindle include?
centrosomes, spindle MTs and asters
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what is checked at the G2/M checkpoint?
is all DNA rep? env favourable?
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what happens in prometaphase?
1) NE breaks fown 2) chrs attach to spindle MTs by kinetochores 3) movement of chrs begin
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what are the 3 classes of MT of the mitotic spindle?
astral, knetchore and interpolar(repel between charges)
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what happens in metaphase?
chrms aligned at equator of spindle at metaphase plate, kinetochore MT attach sister chromatids to opposite poles
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what happens in anaphase?
sister chromatids separate, pulled toward their spindle pole, kinetochore MT shorten by depolymerzing ends and spindle moves apart
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whats checked at the metaphase to anaphase transition?
are all chromosomes attached to the spindle
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what happens in telophase?
2 sets daughter chrs at spindle poles +decondense, new NE form = 2 nuclei,
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what happens in cytokinesis?
the cytoplasm is divided into 2 by a contractile ring of actin and myosin filaments
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what does the entering cell cycle and proceed to S phase check?
is environment favourable
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what kind of signalling operates on cell cycle checkpoints?
negative signalling
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how does the negative signalling work?
unattached chromosomes send negative signals that inhibit progression of cycle
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what do the chromosome send out if they're attached?
positive signal
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what are the nature of the positive and negative signalling?
phosphorylation and proteolysis
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what are the differences between positive and negative signalling?
positive = attached, negative = unattached
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what did cell free frog egg extracts perform mitosis in?
an invitro cell cycle system
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what happened with frog extracts?
took cytoplasm from activated frog eggs and nuclei from sperm, added atp, then cell cycle happens
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what does the fact that the cell cycle grows in cell free invitro system show?
cell cycle control is the cell free cytoplasmic extract
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whats present in the frog cytoplasm that can control the cell cycle?
cyclically activated kinases
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what does cdk need for activity?
cyclin
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what else is cdk regulated by?
phosphorylation/dephosphorylation
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what remains constant through the cell cycle?
cdk
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what changes by synthesis and degradation through the cell cycle?
cyclins
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what enzyme inactivates cdk with cyclin?
wee1 kinase
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what kinase activates cyclin+cdk complex?
cdc25 phosphotase
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is cdk active when it has 1 or 2 phosphates bound?
1
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why does cyclin become inactive with 2 phosphates?
2nd phosphate is an inhibitory phosphate
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what cyclins are there?
G1/S cyclin, S-cyclin, M cyclin
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how are cyclins degraded?
ubiquitin proteasome system
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what does M-cdk trigger?
mitosis machinery
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what does S-cdk trigger?
DNA rep machinery
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when do M-cyclin levels increase?
through G2 and M
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what does M-cyclin levels create?
a pool of inactived M-cyclin complex
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what happens in the late G2 phase to rapidly activate mitosis?
cdc25 activates a positive feedback loop, takes off phosphates and activates cdks
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when is the spindle assembly checkpoint?
metaphase to anaphase transition
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what regulates cyclin levels?
anaphase promoting complex
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what does the anaphase promoting complex do?
control of prtoteolysis, targets other proteins for destruction which induces sister chromatids to separate
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what ubiquitylation enyzmes does anaphase promoting compelx use?
E1 +E2
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what is the activating subnit that makes anaphase promoting complex active to induce ubiuitinylation enzymes?
cdc20
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what controls the metaphase anaphase transition?
proteolysis
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what causes metaphase arrest?
spindle assembly checkpoint chr unattached leads to inhibition of APC and metaphase arrests
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why doesmetapahase arrest?
APC is needed for the ubiquitin proteasome system to degrade M-cyclin to produce anaphase
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what happens if you get unchecked division?
cell death, hyperplasia and cancer
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what happens if you get a withdrawal from the cycle?
replicative senescence, terminal differentation
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what happens if laggingchromosoems or dna damage?
mutations and aneuploidy
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what stages does DNA damage inhibit?
G1/S-cdk, M-cdk
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what cdk does unreplicated dna inhibit?
M-cdk
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APC is inhibited by what?
a chromosome being unattached to spindle
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Other cards in this set

Card 2

Front

what makes up interphase

Back

G1 + Synthesis + G2 phases

Card 3

Front

what happens in the mitotic phase?

Back

Preview of the front of card 3

Card 4

Front

what is the aim of the cell cycle?

Back

Preview of the front of card 4

Card 5

Front

why do cells need to increase in size between divisions?

Back

Preview of the front of card 5
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